NHC–Gold(I) Complexes as Effective Catalysts for the Carboxylative Cyclization of Propargylamines with Carbon Dioxide

Abstract

NHC–gold(I) complexes promote carboxylative cyclization of a range of propargylic amines to afford (Z)-5-alkylidene-1,3-oxazolidin-2-ones in methanol under neutral and mild conditions. The highly active and robust catalyst permits CO2 utilization under a mixed gas atmosphere containing CO or H2. As a key intermediate, a new alkenylgold(I) complex was successfully identified from a stoichiometric reaction of Au(OH)(IPr) and 1-methylamino-2-butyne in THF. The methanol solvent influences the formation of catalytically active cationic gold species and facilitates protodeauration from the alkenylgold complex to release the cyclic urethane product due to in situ generation of methylcarbonic acid in the presence of CO2.